So much of our current knowledge about the neural mechanisms involved in spatial vision has come from studying the visual system of the cat. Neuorphysiologists have examined in detail the spatial properties of neurons at various levels of the cat's visual system, and attempts are now being made to discover the patterns of neural $ connections which give rise to the remarkable degree of stimulus specificity characteristic of these neurons. Advances in the technology of animal psychophysics now make it possible to extend this analysis of spatial vision in the cat to the behavioral level. The proposed research will employ the behavioral technique of conditioned suppression to study several problems concerning the cat's ability to perceive spatial detail: spatio-temporal determinants of contrast sensitivity, the role of lateral inhibition in contrast sensitivity at low spatial frequencies, meridional variations in contrast sensitivity and orientation discrimination, and contrast perception. The general goal is to examine the extent to which spatial vision in the cat, as determined behaviorally, can be related to neural mechanisms within the animal's visual system.